SANTA CLARA -- Justin Smith is riding shotgun in one of the NFL's greatest single-season pursuits of sacks.

"He's chasing history," Justin Smith said of 49ers teammate Aldon Smith, who is five sacks away from Michael Strahan's 2001 league-record of 22﻿1/2.

More sacks could come Sunday when the Miami Dolphins start Stanford-bred rookie Jonathan Martin at left tackle. Martin replaces Jake Long, the 2008 draft's first overall pick who went on season-ending injured reserve Tuesday with a torn triceps.

"I've just got to take advantage of the opportunity," Aldon Smith said.

Martin, a three-year starter at Stanford, started the Dolphins' previous 12 games at right tackle. Coach Joe Philbin, in a conference call with Bay Area media, lauded Martin's poise and work ethic, adding: "This guy hasn't batted an eye."

In the eyes of Justin Smith, however, Martin is merely "a serviceable tackle in the league" who's expected to get help from other blockers to keep the 49ers away from rookie quarterback Ryan Tannehill.

Jim Harbaugh, who coached Martin at Stanford before joining the 49ers last year, credited his former pupil for doing "a good job his entire rookie year."

It's Tannehill, however, who is in the primary sights of Aldon Smith & Co.

Tannehill has been sacked only 23 times. Linebacker Patrick Willis noted that the rookie gunslinger "lets the ball go quick, so we have to make sure we're tight on our coverages."

Philbin complimented the 49ers' secondary as much as Justin Smith for contributing to Aldon Smith's league-leading 17﻿1/2 sacks.

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That total matches Fred Dean's 1983 franchise record. The NFL began tracking sacks in 1982, and since then, no one has compiled more in their first two seasons than Smith's 31﻿1/2.

Smith has had at least one sack in each of the last six games while totaling 13 overall, including 5﻿1/2 on Nov. 19 against the Chicago Bears.

"Aldon got better as last year progressed. Then he just blew up," Justin Smith said. "He's done everything to take his game to the other level."

A year ago, Aldon Smith was the NFL's Defensive Rookie of the Year runner-up while Justin Smith notched All-Pro and Pro Bowl honors.

Justin Smith went a career-long nine games without a sack to start this season, but he has three in the past three games. He also notched a season-best 10 solo tackles in the 49ers' 16-13 overtime loss Sunday at St. Louis.

Beside getting to the quarterbacks, the Smith & Smith tandem hasn't slacked against stopping the run, something that Justin Smith says tends to happen "a lot of times to guys chasing sacks."

"It's all about winning games and getting to the playoffs and the Super Bowl," Justin Smith said. "Hopefully the record falls on the way there."

No, Brett Favre isn't around to give up the record this time as he did in 2001. But it certainly could fall in the 49ers' remaining four games.

After hosting the Dolphins, the 49ers visit two clubs who aren't allowing many sacks, the New England Patriots (19 sacks, 28th most) and the Seattle Seahawks (23 sacks, 23rd most).

The Arizona Cardinals visit the 49ers in the regular-season finale, and they've allowed a league-high 48. But a couple issues could hinder Aldon Smith's pursuit in that Dec. 30 game. A lingering shoulder injury forced him to wear a no-contact jersey in practice Wednesday, as was the case last week. If the 49ers' playoff fate is sewn up before that Cardinals game, they might want to rest him.